1. Field of the Invention
This invention relates to methods, systems and devices for extending the charge of an energy storage device of systems and devices that include a rotating spindle motor. More particularly, this invention relates to methods, systems and devices for converting the kinetic energy of a rotating disk drive spindle motor into electrical energy to charge an energy storage device such as a rechargeable battery of a host device.
2. Description of the Prior Art and Related Information
The growing popularity of portable electronic devices has coincided with significant advances in both the storage capacity of current hard disk drives as well as their miniaturization. Indeed, high capacity disk drives having a form factor of less than two inches are now widely available. The manufacturers of portable devices such as still and video cameras, portable digital assistants (PDAs), music players, telephones and mobile computing devices have taken note and have begun widely incorporating disk drives in the devices they manufacture. In portable electronic systems, the capacity of the rechargeable battery determines the length of time the user may operate his or her system in an uninterrupted fashion. The disk drive of such systems, however, consume a considerable amount of the power supplied by the rechargeable battery. Conventional approaches to lengthening the time during which such systems may operate from the battery tend to concentrate on minimizing the peak power required from the battery with little emphasis on the average running power consumption or total energy utilized.
In mobile devices, the rotating spindle motor of the hard disk drive is often braked when not actively reading or writing or when no reading or writing commands have been received for a predetermined period of time (among other reasons), to save power. The spindle driver electronics in conventional disk drives brakes (i.e., actively decreases the angular speed of) the spindle motor by shorting out the motor windings and dissipating the inertial energy stored in the spindle mechanics in the motor and the driver electronics. This inertial energy is lost as heat that is generated by the inherent resistance of the motor windings and driver circuits, as well as by frictional forces. What are needed, therefore, are ways to use this inertial energy to extend the time the host device may operate from its battery.